EFFLUENT TREATMENT PLANT(ETP)

Prepared by,Md. Alauddin

May, 2016

ETP treats the waste materials into neutralized molecule or reduces the harmful ingredients. Industrial wastewater treatment covers the mechanisms and processes used to treat waters that have been contaminated in some way by anthropogenic industrial or commercial activities prior to its release into the environment or its re-use.

This effluent contains several pollutants, which can be removed with the help of an effluent treatment plant.

ETP treat water and make free from all objectionable impurities present in suspension, colloidal or dissolved form.

Introduction

Stay in compliance Reduce hauling and off-site treatment costs Eliminate municipal fees Reduce supply costs by recovering production materials out of

the waste-stream for re-use Eliminate unnecessary water usage during processing Protection of public health Solving social problems caused by the accumulation of

wastewater For groundwater recharge For industrial recycle

Advantages

Parameter Gov’t StandardsPH 6.5 to 8.5

BOD 30 mg/litCOD 100 mg/litSuspended solids 100 mg/litTDS Approx. 2100 mg/litOil & Grease 10 mg/litChlorides 600 mg/litTemperature 40°C

Effluent Stages

Preliminary Treatment Screens Detritor/scrapers Grit Chamber Skimming Tanks AerationPrimary Treatment Sedimentation/ Settling tank Clarifloculator Equalization Tank Neutralization Tank

Secondary Treatment Activated Sludge Process Trickling Filter Aerated Lagoons Multiple EvaporatorTertiary Treatment Sand/ Membrane Filters Activated Carbon Filters Disinfection Ion-exchange Nutrient Removal

Major Treatment units in ETP

Preliminary treatment removes gross solids and materials that can be easily collected from the effluent and can damage or clog the pumps and skimmers of primary treatment clarifiers.

These are in-organic materials and insoluble organic pollutants (i.e. large floating and suspended solid matter, grit, oil & grease) which are inert and cause problems to further chemical and biological treatments.

The presence and sequence of preliminary treatment units are totally depend upon the characteristic of effluent that is to be treated.

All preliminary treatment consist of physical separation techniques by controlling flow rate of effluent.

Preliminary Treatment

Primary treatment consists of temporarily holding the sewage in a inert basin where heavy solids can settle to the bottom while oil, grease and lighter solids float to the surface.

The settled material go for sludge treatment and floating materials are skimmed off. The remaining liquid is passed to secondary treatment.

Tanks are usually equipped with mechanically driven scrapers that continually drive the collected sludge towards a hopper in the base of the tank where it is pumped to sludge treatment facilities.

At this stage, over 70% of the suspended solids and 40% of the BOD is removed from effluent.

Primary Treatment

Secondary treatment is a biological treatment of effluent which is typically performed by indigenous, water-borne micro-organisms in a managed habitat.

Secondary treatment removes dissolved and suspended organic (bio-degradable) matter by consuming it as a food and convert it into new cell mass, energy and CO2.

The most common micro-organisms are bacteria (aerobic or anaerobic), protozoa and rotifers; least common are fungi and algae.

After secondary treatment almost 70-90% of BOD and 80-90% of dissolved solids are removed from effluent.

Secondary Treatment

Tertiary treatment is the final treatment, meant for ‘polishing’ the effluent and removal of pollutants not removed in primary and secondary treatment.

These pollutants may include soluble inorganic compounds such as phosphorous or nitrogen which may support algae growth in receiving waters.

Also removes organic materials contributing BOD, COD, color, taste, odor; bacteria, viruses, colloidal solids contributing turbidity; or soluble minerals which may interfere with subsequent re-use of the wastewater.

Preferred when treated water is need to be reuse or discharge is into a highly sensitive or fragile ecosystem (estuaries, low-flow rivers, coral reefs, etc).

Tertiary Treatment

Tertiary treatment add additional cost to the treatment process but produce high quality effluent which can be reuse further for commercial and industrial applications.

Treated water can be reuse for the irrigation of a golf course, green way or park, construction work, industrial process, etc. If it is sufficiently clean, it can also be used for groundwater recharge.

Treated water is sometimes disinfected chemically or physically depending upon the discharging location.

Tertiary Treatment

Equalization: The raw waste from the main plant is first collected in the equalization tank through screening.The equalization tank is designed for a hydraulic retention time of around 6 hours and is avoided with air grids connected to air blowers for maintaining the solids is suspension

Effluent Mixer Flocculation Tank & Clarifier: The equlized waste is then pumped into the flask mixer compartment of flash mixer & flocculation tank where coagulant is dosed and polymer in the flocculation compartment to aid the process of settling. The overflow from the flocculation compartment is taken into the clarifier for removal of suspended solids and BOD/COD.The overflow from the clarifier is taken for further treatment while the underflow is taken for sludge compartment.

Process Description

Biological Treatment: The neutralized effluent will this the treated through the Bio Tower with aeration tank and clarifier. The liquid overflow from the Lamella clarifier is taken to the chlorination tank. The sludge underflow from the Lamella clarifier is partially returnedto the inlet of the aeration tank for maintaining the desired level. The excess sludge is treated through a basket type centrifuge.

Filtration: Chlorinated water will be passed through a Multigrade Sand Filter for further reduction of suspended solids to less then 20 ppm and then passed through a activated carbon filter for the polishing of BOD, COD values.

Process Description

Sludge Treatment: The under flow from the clarifier and the secondary clarifier having a sludge consistency of around 1-1.5% is pumped into the centrifuge for dewatering. The dewatered sludge is then disposed off suitably while the concentrate is taken back to the equalization tank

Process Description

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